WALTHAM — In all his years as a coach, Doc Rivers never saw losses eat at a player the way they did Darrell Armstrong.

Armstrong was far and away the 100-beat-per-minute heart of the Orlando Magic the four years Rivers coached there. When they won, he was the player hopping on tables to celebrate. When they lost, he was the one that sunk into the seven stages of grief.

The weight of the game didn’t matter. Even if it were a regular-season loss, he was in tears.

“I’ve never had a player like that,” Rivers said. “He cried 30 times, and that’s no exaggeration. I’m talking about times you had to take him out of the locker room.”

The next day, it was like it never happened.

“He was up and ready,” Rivers said.

The Celtics coach has had rosters scattered within emotional landmines. Kevin Garnett is the poster child for frightening intensity before games, euphoric celebration after big wins, and stone-cold intolerance for losses.

Armstrong, though, was a rare breed.

“Kevin is close to that emotional,” Rivers said. “But not to that level.

“I don’t mind that in a guy, but I don’t expect that from everyone. I just think everyone has a different emotion, a different way of handling things.”

Sitting on a stack of exercise mats, staring blankly at the court before practice Thursday, was Rajon Rondo. The Celtics lost Wednesday night on their home floor against the Grizzlies — their fourth straight loss — and Rondo seemed to wear all of the losses on his face.

This is the second time this season the Celtics have lost at least three in a row. They have lost eight of their last 10 games, and they’re three games under .500 for the first time since last Jan. 22.

Except for his rookie year, Rondo could have counted the number of three-game losing streaks he had experienced on two hands before this season. The toll these losses are taking on him is clear.

“I’m a sore loser — it’s tough to lose,” said Rondo. “Everybody isn’t. You’ll learn that everybody isn’t a sore loser. Some teams are OK with losing. Some guys are OK with just getting a check.

“But everything I do, I compete. So this four-game losing streak is frustrating.”

The point guard stopped short of pointing fingers.

“I can only judge myself,” Rondo said. “That’s my New Year’s resolution: I don’t want to judge anybody this year.”

And there is no reason to, according to his coach. There is no way to tell, Rivers said, how much a loss affects a player based solely on an emotional eye-test.

“Honestly, I don’t look, don’t notice,” Rivers said. “I don’t know what that does. You’ve still got to learn from losing and learn from winning at the same time.

“Clearly, there are guys that are more emotional than others. That doesn’t mean the other guys don’t take it just as poorly.”

As the team tries to push through a rough stretch, Rivers said, there are players such as Jared Sullinger and Jeff Green who don’t wear their hearts on their sleeves, but it doesn’t mean they’re unaffected.

“If you read how a team was winning or losing, you couldn’t get a read from Jared,” said Rivers. “You’d be wasting your time. Jeff is the same way. But you can see it on Kevin. You can see it on Rondo.

“That’s why you don’t try to read into how guys take losses. Some guys take losses by laughing and trying to get into another universe. Some guys want to stay in the loss.

“You just have to stay away from it.”

What concerns Rivers more is the fact that the Celtics haven’t figured out ways to string wins together.

“It’s nothing you want,” Rivers said. “You don’t want to lose two or three in a row, let alone three or four, but what’s more troubling for me right now is we haven’t won more than two in row. That bothers me more in some ways than losing four in a row.

“To me, it points to what I’ve been saying all year with our consistency. We just haven’t been able to stay with what we’ve done to win games and do it over again.”

Every season since raising their 17th championship banner in 2008, the Celtics have run into some turbulence but have figured out ways to recover.

That includes Danny Ainge. After the Grizzlies game, Ainge and Rivers got to comparing this year to last year, and Ainge said, “It was worse last year.”

Rivers’s response: “That was last year. It doesn’t matter what happened last year.

“Every team’s different, and you can’t push the button from the past years or any year and assume that it’s going to come — at least no coach can.

“Every year’s hard in that way. Every year you fight to get the guys back into their roles, buy into your system, buy into less minutes. There’s so many things guys have to do. So I don’t think any year’s harder.”